Africa is the first region into which Islam is carried by merchants rather than armies. It spreads down the well-established trade routes of the east coast, in which the coastal towns of the Red Sea (the very heart of Islam) play a major part.

There is archaeological evidence from the 8th century of a tiny wooden mosque, with space enough for about ten worshippers, as far south as modern Kenya - on Shanga, one of the islands offshore from Lamu. Shanga's international links at the time are further demonstrated by surviving fragments of Persian pottery and Chinese stoneware.

By the 11th century, when Islam makes its greatest advances in Africa, several settlements down the east coast have stone mosques.

At Kilwa, on the coast of modern Tanzania, a full-scale Muslim dynasty is established at this period. Coins from about 1070 give the name of the local ruler as 'the majestic Sultan Ali bin al-Hasan'. Three centuries later the Muslim traveller Ibn Batuta finds Kilwa an extremely prosperous sultanate, busy with trade in gold and slaves. In the 20th century Muslims remain either a majority or a significant minority in most regions of the east African coast. But the early penetration of Islam is even more effective down the caravan routes of west Africa.

Islam in west Africa: 8th - 11th century

From the 8th century Islam spreads gradually south in the oases of the Sahara trade routes. By the 10th century many of the merchants at the southern end of the trade routes are Muslims. In the 11th century the rulers begin to be converted.

The first Muslim ruler in the region is the king of Gao, from about the year 1000. The ruling classes of other communities follow suit. The king of Ghana, the most powerful realm, is one of the last to accept Islam - probably in the 1070s.

The effect of Islam on African communities, with their own strong traditional cultures, is a gradual process. In 1352 Ibn Batuta visits Mali, the kingdom which in effect replaces Ghana. He is impressed by the people's regularity in saying their prayers, but he looks with stern disapproval at certain practices which are more evidently African.

He particularly frowns upon performances by masked dancers, and on the tendency of women to walk about in an unseemly shortage of clothing. Nevertheless the influence of Islam on this part of Africa is profound. From the Sudan to the Atlantic, the entire region north of the equatorial forests remains to this day largely Muslim.

Muslims from Ghazni: 10th - 11th century

The long-standing threat to India from Muslim invaders is renewed when an aggressive Turkish dynasty wins power in Ghazni, southwest of Kabul. On several occasions Subuktigin, the first of these Ghazni rulers, makes raids on the region around Peshawar. Under his son, Mahmud, expeditions into India become a regular policy. During a 33-year reign, the number of his campaigns in the subcontinent is somewhere between twelve and seventeen.

Many of them are sorties for plunder and booty among the riches of India, sometimes as far down the Ganges as Kannauj. But Mahmud's most famous undertaking, in 1025, is different in kind. It is undertaken in a mood of religious zeal as much as for plunder.

India is the first place where invading Muslims are confronted with a highly developed cult of idolatry. The Hindu profusion of sculpted gods and goddesses, often provocative or weird in the disposition of their limbs, is well calculated to outrage any attentive reader of the Qur'an - with its prohibitions against idols and graven images. Mahmud's strenuous effort in marching an army across the desert south from Multan, in 1025, has a holy purpose.

His destination is the great temple at Somnath, where Shiva's linga is washed daily in water brought by runners from the Ganges.

The temple has 1000 Brahmin priests and 600 musicians, dancers and other attendants. Countless pilgrims bring it vast wealth (the removal of which adds to the pleasure of pious indignation). When Mahmud arrives to destroy the place, it is said that 50,000 Hindus die in defence of it. No trace is allowed to remain of the building or its sacred contents.

In the annals of Muslim India, Mahmud acquires a heroic status for this act of destruction. It is the first in the long series of sectarian outrages which have marred the 1000-year relationship between Muslims and Hindus.

Since most of Mahmud's expeditions have been in the nature of raids, he and his heirs never extend their control beyond the Punjab - the territory closest to Afghanistan. But this foothold beyond the Khyber Pass gives easy access to the rich north Indian plain. In leaving the door ajar, Mahmud creates an opening for countless Muslim adventurers from central Asia.

This northwest region of the subcontinent will never again be Hindu. For the next five centuries, Muslim marauders push eastwards through the Punjab to find their fortunes in India. Some of them (in particular the Moghuls) settle down as the most spectactular of India's rulers.

Muslim Malaya and Indonesia: from the 13th century

Islam's final push to the east derives from the strength of Muslim India. By the end of the 13th century Indian merchants from Gujarat, trading through the Straits of Malacca, have established Muslim settlements in northern Sumatra; they are noted by Marco Polo.

The wealth and sophistication of these traders brings converts to Islam, and the influence of the religion becomes rapidly stronger after a Muslim sultanate is established in Malacca from 1445. The threat of conquest and the benefits of trade now provide two good reasons for the neighbouring communities to embrace the Muslim faith.

During the 15th and 16th centuries Islam spreads through the Malay peninsula and the islands of Sumatra and Java. By the 17th century the Hindus, with their warrior princes, brahmin priests and caste system, are confined to the eastern tip of Java. Soon they are ousted even from there.

They cross to Bali, where they and their traditions manage to survive. By this time the mainland regions from Burma to Cambodia have resolved centuries of indecision between Hinduism and Buddhism. They have chosen Buddha. The small island of Bali becomes, as it remains to this day, the only Hindu outpost in a southeast Asia otherwise divided between Buddhism and Islam.

Three Muslim empires: 16th - 18th century

By the mid-16th century the broad sweep of the Muslim world, from the Atlantic coast of north Africa all the way to India, has settled down as three powerful neighbouring empires.

In the west, occupying roughly the extent of the Byzantine territory before the Arab conquests of the 7th century, is the Ottoman empire with its capital in Istanbul. In the centre is the Safavid dynasty of Persia, passionately committed to the doctrines of The Shi'as in opposition to the Sunni orthodoxy of the Ottoman Turks. In the east is the Moghul empire, covering the greater part of India. It differs from the others in that its Muslim ruling class is a minority in an infidel population.

There is frequent border warfare between Persia and its neighbours on either side, but for a century and more the three regions are relatively stable and prosperous.

Then, during the 18th century, Persia is shaken by internal conflicts, bringing three new dynasties within fifty years. At the same time there are external threats, from European powers, to the Ottoman and Moghul empires. The Turkish sultans acquire a powerful and hostile neighbour in the form of the expanding Russian empire. India finds itself drawn gradually and inexorably into the British empire.